In general, applications of optical elements including light emitting diodes (LEDs) as next generation illumination sources have been gradually increased. Among these, an LED is a kind of semiconductor element which converts electrical energy into light energy using characteristics of a semiconductor formed of a specific compound, has high light conversion efficiency and thus achieves energy consumption reduction of up to 90% at maximum as compared with conventional illumination, such as incandescent lamps and fluorescent lamps, has a small size and is thus proper for miniaturization and lightweight trends, is capable of being infinitely expanded, and has a semi-permanent lifespan.
Further, since the LED has advantages that it does not execute thermal light-emission or discharge light-emission and does not require pre-heating and thus has fast response time and a simple lighting circuit, and does not use a discharge gas and a filament and thus has high impact resistance and is safe, scarcely causes environment pollution, executes high repetition pulse operation, decreases fatigue of the optical nerve and executes full color realization, the LED is widely used in various digital products or home appliances and peripheral devices. Particularly, as a high luminance LED solving a low luminance problem of the conventional LED comes onto the market, purposes and usages of the LED are expanded.
Particularly, since a white LED is very useful as indoor and outdoor illumination, the frequency of use of the white LED is rapidly expanding and it is predicted that the white LED will dominate the illumination market soon because the government promotes a plan of raising the supply rate of the white LED in consideration of high energy efficiency and environmentally friendly advantages of the white LED together with a tendency to replace incandescent lamps with fluorescent lamps.
Given the rapid speed of development of techniques using LEDs, it is judged that LEDs will graft onto streetlamps installed on a road through which persons and vehicles pass and used to allow pedestrians and vehicles to efficiently walk on and pass through the road at night.
Conventionally, illumination lamps for streetlamps are formed of a heavy metal harmful to the human body, such as halogen or mercury, and these lamps have a short lifespan and are periodically replaced and thus require considerable expenditure and effort for maintenance and repair. Therefore, high power LED lamps reducing power consumption and having excellent illumination performance are widely used now. The high power LED lamps have a long lifespan and remarkably reduce power consumption to save energy while having high brightness as compared to a general halogen or mercury lamp.
However, the high power LED lamps generate high heat in operation, and such heat influences peripheral parts as well as the high power LED lamps and thus may cause malfunction thereof or reduction in the lifespan thereof.
That is, an optical element using light sources, such as LEDs, is essentially a semiconductor element, and is thus relatively weak to heat as compared to light emitting elements, such as incandescent lamps or fluorescent lamps. Therefore, when junctions within the semiconductor element maintain a constant temperature, the semiconductor element may maintain the original advantages thereof, such as high light emitting efficiency and long lifespan. That is, in case of an LED, the LED may maintain the original advantages thereof if the temperature of junctions of the semiconductor element maintains 85° C. or less always.
Therefore, research on techniques relating to optical elements, such as LEDs, to improve light emitting efficiency of LED chips and to efficiently extract the light emitting efficiency and research on application of optical element light sources to various fields have been conventionally carried out. However, as heat generated from an optical element during driving directly influences optical efficiency of the optical element light source and the optical element is applied to high power lamps, problems due to generated heat become serious.
Accordingly, a structure of an optical element in which a heat dissipation plate serving to dissipate heat generated during driving of the optical element is connected to a semiconductor element has been proposed.
In relation to such a heat dissipation plate applied to LEDs, Korean Utility Model Registration No. 20-0448163 discloses a heat dissipation plate for LED lamps which is installed on an LED lamp. Such a heat dissipation plate for LED lamps includes at least one heat dissipation fin connected to a case of the lamp and formed on the upper portion of the heat dissipation plate to have a sufficient heat dissipation area, a support to fix a circuit board on which at least one LED is mounted, at least one connection fixing groove formed on the lower portion of the heat dissipation plate so that the support is inserted into the at least one connection fixing groove, and a fixing screw to fix the circuit board to the support, the support includes at least one screw hole formed at a designated interval along the center of the support, the circuit board includes at least one tightening hole formed along the center of the circuit board so as to correspond to the at least one screw hole of the support, the at least one LED is arranged between the at least one tightening hole and is installed integrally with the heat dissipation plate for LED lamps by fixing the circuit board to the support by combining the fixing screw with the at least one screw hole and the at least one tightening hole, the at least one heat dissipation fin is formed integrally with the at least one connection fixing groove, and the heat dissipation plate for LED lamps is formed of an extruded product using aluminum and may thus minimize heat resistance and maximize heat dissipation effect.
Further, in relation to a streetlamp to which LEDs and a heat dissipation plate are applied, Korean Utility Model Laid-open Publication No, 20-2008-0003317 discloses a cooling apparatus of a high power LED lamp streetlamp having an LED lamp assembly provided with a plurality of high power LED lamps. Such a cooling apparatus includes a thermally conductive heat collecting plate provided with an adhesive surface attached to one surface of the LED lamp assembly opposite the high power LED lamps and including a receipt groove part formed on the other surface of the heat collecting plate, a heat exchange tub combined with the receipt groove part of the heat collecting plate and accommodating a liquid heat medium executing heat exchange with the thermally conductive heat collecting plate, and a plurality of thin heat dissipation plates separated from the outer circumferential surface of the heat exchange tub by a designated interval and executing heat exchange with the heat medium in the heat exchange tub, and increases exchange and dissipation performance and efficiency of high heat generated from the LED lamps, thus improving cooling performance of the LED lamps and preventing malfunction of the lamps and peripheral parts or reduction of lifespans thereof due to heat.
However, the above-described conventional heat dissipation plates merely exhibit a function of dissipating heat, generated from semiconductor elements due to light emission of optical elements, to the outside, and such heat is only dissipated to the outside but is not used as energy. Recently, as problems due to lack of resources become more serious, solutions to conserve resources are urgently required and development of techniques to improve requirements for using waste heat inevitably generated in the optical element field having a high application degree are required.